Interior Lighting: Overview Ford Thunderbird XI

The interior lighting system consists of

1. left and right front dome/map lamps
2. deck lid lamp
3. glove compartment lamp
4. driver and passenger footwell lamps
5. front electronic module (FEM)
6. rear electronic module (REM)
7. instrument cluster

Refer to INTERIOR LIGHTS for schematic and connector information.

Scheme 1

Principles of Operation

Note. The front electronic module (FEM) and rear electronic module (REM) must all be reconfigured when installing a new module. Refer to MODULE CONFIGURATION EXTXREF Section 418-01 .

The vehicle's electronic functions are divided into zones. The FEM controls the front portion of the vehicle and the REM controls the rear portion of the vehicle. These systems rely heavily on the standard corporate protocol (SCP) communication network in order to transmit and receive signals. As a technician, it is very important to understand

1. where the input (command) originates from.
2. all information (messages) necessary in order for a feature to operate.
3. which module(s) receive(s) the input or command message.
4. whether the module which received the input (message) controls the output of the feature, or whether it outputs a message over the SCP communication network to another module.
5. which module controls the output of the feature.

FEM Operation

This system is unique in that many of the inputs the FEM receives are delivered via the SCP communication network. These input messages come from other modules connected to the network, such as the REM and instrument cluster. The FEM will interpret the inputs and, in turn, command the correct output. The FEM also receives inputs which come directly from components which are hardwired to the module, such as the passenger door ajar switch.

The FEM controls the outputs to all interior lighting. The interior lamps include: interior lamps, dome lamps, and map lamps. The lamps will be illuminated if the driver or passenger door is ajar. The switches are hardwired to the FEM. When any of the two doors are opened, the FEM will command the interior lamps through the SCP network to the FEM.

All interior lighting is powered by the switched system power (SSP) feature (refer to SWITCHED SYSTEM POWER ). A failure of any or all of the SSP feature(s) could cause inoperative interior lighting. When diagnosing the interior lighting, it is essential to determine if all relative symptoms and DTCs are controlled by the SSP feature.